feat(fee): export resolveFee and document fee / feeMultiplier precedence (closes #606)

[Ranjeet2063]

Summary

Re-exports resolveFee from the primary SDK entry point (src/index.ts) and documents the fee precedence hierarchy in README.md, ensuring consumers can inspect or customize inclusion fee resolution before transaction construction (closes #606).

Key Changes

• src/index.ts:
  • Re-exported resolveFee alongside getServer and clearServerCache.
• README.md:
  • Added dedicated Fee Resolution & Precedence section detailing the three-tier resolution order:
    1. Explicit config.fee (highest precedence, returned as-is).
    2. config.feeMultiplier (BASE_FEE * feeMultiplier when fee is undefined).
    3. Fallback to default BASE_FEE (100 stroops).
  • Formatted ConduitConfig Reference table for clean markdown rendering.
• src/tests/soroban-fee-config.test.ts:
  • Added assertion confirming resolveFee is directly importable from the SDK root entry point and behaves identically.

Verification

• npx vitest run src/tests/soroban-fee-config.test.ts: 6/6 tests passing.
• Full test suite: 82/82 active test files passing (1,025 passed).
• Production build: npm run build (Clean rollup ESM and CJS bundle creation).

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.